Momac

That doesn't make it legal to use in a narrowboat

I suspect its low sulphur fuel they are selling.

https://canalrivertrust.org.uk/media/document/Irv6ssbjIVxJQIjqHLO8-A/sfnTQI7xeJJBmGwOY5xSSzWnXHP1o_Vvx1a1t9o3b_I/aHR0cHM6Ly9jcnRwcm9kY21zdWtzMDEuYmxvYi5jb3JlLndpbmRvd3MubmV0L2RvY3VtZW50Lw/0189917d-1f87-73c9-9b4a-9c4ddcb6fab7.pdf

Can that legally be used in a pleasure craft like a narrowboat?

Boats inthe EU have been using white diesel for some years. As far as the engines are concerned there is no difference between red and white. Some suppliers like BP do offer a higher cetane grade of diesel .I doubt this is used for making red by adding dye. Fuel additives are available which may enhance the cetane number. I don't really understand why red diesel is still available in the UK. The availability of red diesel seems an avoidable complexity.

Red is simply White with dye added

You can probably tell the build quality of new motorhomes from the weight and the new price. Certainly some brands are better than others just like everything else. A neighbour has bought an Adria motorhome which I see is priced new at over £100k

The council put a stop to camping at that location. Boat sales seem to have declined local to me although the cheaper end of the market seem to be doing okay. I have seen some big reductions in asking prices for the more expensive boats . The post covid price jump seems to have evaporated. As for boat movements must confess we have not been very far at all in April , due mostly to the weather which has not been to the chief officers liking. I am expecting a rush of boats moving over the coming bank holiday weekend as the weather forecast looks reasonable (at the moment). The hire boat prices mentioned above made me think the cost of keeping my own boat not so bad after all.

That could work for someone who lives elsewhere but works in London 5 days a week and just wants somewhere to sleep. eg Travels to London Monday morning and works then stays overnight Monday to Thursday leaving after work Friday to return to their out of town home.

Probably best to stand the engine on polythene sheet and use some timbers around the edge and under the sheet to form a bund. Then use the degreaser with a brush . A roll of paper towels to mop up. Thankfully the marina here provides good waste disposal facilities including bins /tanks for items like used engine oil ,oily rags, oily water , removed fuel filters and oil filters . So responsible disposal is not a issue .